1. Field of the Invention
The invention is concerned with new thiadiazole derivatives and their use as lubricant additives. More particularly the new thiadiazoles are derived from 2,5-dimercapto-1,3,4-thiadiazole and certain other moieties, such as the organophosphorus moiety.
2. Description of the Prior Art
Lubricants are prone to oxidative deterioration when subjected to elevated temperatures or even when they are exposed to atmospheric conditions for long periods of time. Such deterioration of lubricants, including lubricating oils and greases, produces sludge and gums, causes metal parts to corrode and produces loss of lubricating properties of the oil. Many prior art additives are only marginally effective except at unacceptably high concentrations, especially when the lubricants are subjected to drastic oxidizing conditions.
Sulfur containing compounds are widely used as EP additives in lubricants for gear oils and the like. However, they have the disadvantage of tending to corrode metal parts, especially bearings which may contain copper, silver or other sulfur-reactive metals. Consequently, the amount of such additives that can be used is a compromise between maximum EP effectiveness and minimum corrosivity. This problem of balance often becomes quite serious.
It is known that such compounds as ##STR1## EFFECTIVELY INHIBIT THE CORROSION OF SILVER AND COPPER BY ACTIVE SULFUR COMPOUNDS. However, the parent 2,5-dimercapto-1,3,4-thiadiazole lacks solubility in lubricants and for that reason has limited applicability as an anticorrosion agent.
The herein disclosed derivatives of 2,5-dimercapto-1,3,4-thiadiazole are not only lubricant-soluble, but they also exhibit good multifunctionality in that they are excellent anticorrosion agents and impart load carrying properties to the lubricant.